A particularly promising application of such a method is for example the analysis of biological samples such as blood or plasma samples in order to extract therefrom biological parameters such as a mass spectrum estimation for revealing molecular concentrations of proteins. Knowledge of this mass spectrum and/or these concentrations makes it possible to detect abnormalities or illnesses. In particular, it is known that some illnesses such as cancers, even at an early stage, may have a possibly detectable impact on the molecular concentrations of certain proteins. The study of these proteins, referred to as proteomics, thus becomes an essential element in many fields in medicine. This is because proteins are particularly interesting cases of biomarkers that describe both the expression of genes and the influence of the environment and are more accessible in a good number of organic fluids (blood, serum, urine, biological fluid, lysate of a biological sample, etc). However, more generally, the analysis of samples for extracting relevant molecular mass parameters affording for example an aid to the diagnosis of a state (health, pollution, etc) that can be associated with these samples is a promising field of application of a method according to the invention.
Among the concrete applications that can be envisaged, the following may be noted: the biological analysis of samples by detecting proteins and their masses; the characterization of bacteria by mass spectrometry; the characterization of the state of pollution of a chemical sample (for example the analysis of a gas in an environment or the analysis a heavy metal in a liquid sample). The relevant parameters extracted may comprise mass spectra of components such as molecules (peptides, proteins, enzymes, antibodies, etc) or molecular assemblies. Molecular assembly means for example a nanoparticle or a biological species (bacterium, microorganism, cell, etc).
In the case of a biological analysis by detecting proteins, the entire difficulty is arriving at the most precise possible estimation in a noisy environment where the proteins of interest are sometimes present in the sample in very small quantities.
In general, the sample passes through a processing chain comprising at least a mass spectrometer. This processing chain is designed for the supply of a signal representing masses of components in the sample according to a mass/charge ratio in the mass spectrometer.
Optionally, the processing chain may comprise, upstream of the mass spectrometer, making it necessary for the sample to be in nebulized gaseous phase, a vaporizer and an electrospray (or equivalent, in order to carry out ionization and/or desorption of the components of the sample) able to proceed with the phase change necessary when the sample to be analyzed is for example available in liquid or solid phase.
Finally, when the mass spectrometer used has a MEMS (Micro Electro Mechanical System) or NEMS (Nano Electro Mechanical System) electromechanical sensor, the processing chain may optionally comprise focusing electronics, for example a hexapole, guiding the ionized components through a chamber at very low pressure. MEMS Sensors are used for compounds with high molecular masses, for example molecular assemblies, while NEMS sensors are used for detecting compounds with lower molecular masses, for example single molecules.
The major advantage of using a mass spectrometer with a MEMS or NEMS electromechanical sensor in the processing chain is to allow a quantification and estimation of the mass parameter (for example the mass or mass spectrum) at the level of the single component. The mass spectrometry task is then carried out in counting mode, which gives rise to great sensitivity and a reduction in the measurement noise.